1. Field of the Invention
This invention relates to a loudspeaker, particularly to a moving iron unit applied in earphone and other miniature loudspeakers, within the field of electro acoustics and micro mechanics.
2. Description of the Related Art
In the moving iron earphones in the market today, the moving iron unit works by the basic principle of electronic conversion, in which the AC signals go through the magnetic induction coil, which becomes magnetic by induction and magnetizes (polarizes) the balanced armature in the middle of the coil, and the magnetized (polarized) balanced armature vibrate up and down between two permanent magnets by the principle of “likes repel and opposites attract”. The sound-generating diaphragm of the moving iron unit is changed in such a manner that a metal transmission rod is connected with the balanced armature, whose vibration up and down drives the diaphragm to vibrate up and down, thereby to boost the air in the cavity of the earphone to generate sounds. However, the existing moving iron earphone is generally troubled by shortcomings such as low conversion efficiency, insufficient high/low frequency response, low response speed, serious harmonic distortion, and susceptibility of acoustic fidelity to humidity changes. In particular, the common U-shaped, E-shaped and flat balanced armatures (refer to FIGS. 1-3), which are usually seen in market today, all have the weakness of poor mechanical shock resistance.